Method of rolling slabs in planetary mill



Jan. 21, 1969 s. ORR ET AL 3,422,656

METHOD OF ROLLING SLABS IN PLANETARY MILL Filed March 18, 1966 Sheet of 2 INVENTORS HOWARD S. ORR ANTHONY D.REINHARDT ATTORNEY Jan. 21, 1969 H. s. ORR E AL A METHOD OF ROLLING SLABS IN PLANETARY MILL Filed March 18, 1966 FIG.5

Sheet 2 of2 INVENTO HOWARD S OR; ANTHONY D.REINHARDT ATTORNEY United States Patent Claims ABSTRACT OF THE DISCLOSURE A method of hot rolling a slab to strip thickness comprising edge rolling the slab in a pair of grooved rolls defining a convexly edged pass which is so dimensional as to be fully filled by the slab cross section so that the slab possesses convex edges, and then reducing the slab to strip dimensions in a planetary mill while preserving thereon the convex edges. This method eliminates the lamination of the strip edges and hence trimming of the strip.

The present invention relates to hot strip mill rolling processes in which a metal slab is hot rolled into a sheet or strip. More particularly, this invention relates to a novel edge rolling method for hot strip mill rolling processes.

The planetary mill has proved to be an efficient apparatus for hot rolling metal slabs to sheet or strip thickness. A single planetary mill is capable of replacing a half dozen finishing stands in a conventional hot strip mill. In the usual planetary rolling operations, a slab is heated in a reheat furnace, extracted therefrom by pinch rolls, and then delivered to an additional set of rolls which feed the slab into the planetary mill. The sheet or strip product as it emerges from the planetry mill has edges which are generally laminated but in some instances concave. Either edge configuration is undesirable, and the edges of the product must be trimmed before the product can be sold or further processed.

An object of this invention is to provide an edge rolling process in which the edges of a metal slab are hot rolled to a convex configuration before the metal is rolled to sheet thickness, so that the resulting metal sheet or strip will have edges which are either square or slightly convex and which will therefore not require trimming before the metal can be sold or further processed.

According to this invention, a metal slab from a slab heating or reheating furnace is passed at hot rolling temperature through a vertical edging roll stand having a pair of edging rolls, each' of which includes a groove formed by a pair of sloping (i.e., frusto-conical) surfaces having an included angle of 100 to 130 therebetween. The pass defined by the rolls shapes the edges of the slab to a convex configuration. Subsequent rolling of the slab to sheet thickness in a planetary mill preserves this convex edge intact, so that no further trimming of the edges is required.

An included angle of 100 to 130 between the two sides of the groove is important. If the included angle is less than about 100, the metal slab cannot fill the pass and the desired edge shape is not obtained. If the included angle is greater than about 130", the convexity imparted to the edge is not sufiicient to give an edge of the desired convex configuration after rolling to sheet thickness.

This process is particularly useful in rolling steel, and will be described with particular reference to steel. However, other metals such as titanium can also be rolled according to this invention.

This invention will now be described further with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation of a hot strip mill "ice which includes a pair of vertical edging rolls for rolling the slab edges to the desired convex configuration according to this invention;

FIG. 2 is a fragmentary vertical sectional view of the edger rolls and a slab passed therebetween;

FIG. 3 is a fragmentary detail showing the grooved pass in the vertical edging rolls of this invention;

FIG. 4 is a vertical sectional view taken through a finished strip which has been rolled according to this invention;

FIG. 5 is a front elevational view of a vertical edging roll stand according to this invention, showing the edging stand and a portion of the drive mechanism therefor; and

FIG. 6 is a sectional view looking downwardly along line 6-6 of FIG. 5, showing a section through the shaft coupling for driving the edging rolls.

Referring now to FIG. 1, a steel slab is heated to a temperature in the range of about 2000 to 2400 F., and generally to about 2200 F., in reheat furnace 12. The slab is supported on rollers 13 in furnace 12. The slab is supported on table rollers 14 as it continuously travels from furnace 12 to a vertical edging roll stand 15 in which the edges of the slab 10 are hot rolled according to this invention. Edging roll stand 15 comprises a pair of power driven vertical edge holls 16, each of which has a grooved pass 17 in which the edges of the slab are rolled to a convex configuration. The slab 10 is guided into vertical edging roll stand 15 by entry guides 20. The edge rolls 16 not only roll the edges of the slab to the desired convex configuration, but also crack scale on the edges of the slab or on the top and bottom surfaces of the slab adjacent to the edges. Such scale may be formed in reheat furnace 12. The edge rolls 16 also roll the slab to a uniform width.

After the edges of the slab 10 have been shaped and scale cracked in vertical edging r-oll stand 15, the scale is removed by water sprays 21 located above and below the pass line of slab 10. The slab then travels to a planetary mill which comprises a pair of feed rolls 22 above and below the slab, and one or more pairs of planetary rolls 23 which roll the slab 10 to sheet thickness. The product emerging from the planetary mill, which is generally in the form of a long continuous strip, may be water cooled and coiled on a conventional coiler. This product has convex edges, as shown in FIG. 4, and is saleable Without edge trimming.

The process of this invention is particularly suited for edge rolling of slabs having a thickness of about 1.5 to about 6.5 inches. The slabs may be edge rolled in their as-cast thickness, although more frequently the slabs as cast have a greater thickness and are rolled to a thickness in the above-stated range of 1.5 to 6.5 inches prior to entering reheat furnace 12. Slabs thicker than 6.5 inches can be edge rolled, although this is often undesirable in view of the large size and power requirements of the equipment. Slabs seldom are thinner than 1.5 inches when edge rolled according to this invention. Rolling of such thin slabs, particularly if they have a high width-to-thickness ratio in excess of about 10:1, is apt to cause bulging in the thickness direction near the edges of the slab, producing a slab whose cross-sectional shape resembles a dog bone.

The configuration of the edging rolls may be seen best in FIGS. 2 and 3. Each roll 16 includes a. groove 17 formed by a pair of inwardly sloping surfaces 25 and 26 joined together by a rounded portion 27. A pair of collars 28 and 29 respesctively above and below groove 17 confine the slab 10 to the groove. Lower collar 29 may have a step 30 as shown in the drawings, although the step is not necessary. The side walls 31 and 32 of collars 28 and 29 respectively have a small slope, converging slightly going from the respective collars 28 and 29 radially inward toward groove 17, in order to facilitate entry of a slab into the groove. Rounded corners 33 and 34 connect collar side walls 24 and 25 with the adjacent sloping surfaces 18 and 19 respectively.

The dimensions which are essential to proper performance of rolls 16 will not be explained with reference to FIG. 3. As stated earlier, the sloping surfaces 25 and 26 of groove 13 have an included angle of 100 to 130 therebetween. This included angle is denoted by a FIG. 3. If this angle or is less than 100, the steel will not fill the roll pass. If ,u. is greater than 130, the amount of convexity imparted to the edges of the slab is not sufficient to give the desired convex configuration in the strip rolled from the slab.

The pass width p, which is the distance between the intersections of sloping surfaces 18 and 19 with the adjacent collar side walls 31 and 32 respectively, is about 1.5 to about 6.75 inches. The pass width p is preferably slightly larger than the thickness of the slab, and the range of pass widths indicated is ideal for rolling slabs of 1.5 to 6.5 inches in thickness. As an example, when the slab thickness is 3.75 inches, the preferred pass Width is about 3.88 inches.

The included angle a varies slightly with pass width p, becoming slightly greater as the pass width is increased. This included angle a will nearly always be in the aforesaid range of 100 to 130 when the pass width p is in the range of 1.5 to 6.5 inches.

The radius r of the rounded surface 27 which joins sloping surfaces 25 and 26 is in the range of 1 to 1.25 inches, and a thickness of about 1.19 inches is preferred. The rounded corners 33 and 34 have radii t of about 0.5 to about 0.75 inch, preferably about 0.62 inch. Sides 31 and .32 have a slope angle of about 8 to 12 with respect to the horizontal.

Referring now to FIG. 5, the edger roll stand and a drive mechanism for driving the edging rolls 16 are shown as they appear looking in the direction of travel of a slab. The edging rolls 16 are journaled for rotation in U-shaped roll chocks 40, each of which has horizontally extending arms above and below the roll 16. The right hand roll chock 40 is horizontally movable so that the distance between rolls 16 can be varied. This makes it possible to roll slabs of different widths. For example, the distance between rolls may be varied from about 16 to about 32 inches. The illustrated mechanism for varying the distance between rolls includes a threaded shaft 41, a gear reducer 42, and a motor 43 for driving the threaded shaft. Other mechanisms, such as a hydraulic ram, can be used if desired. Both roll chocks 40 are movable, although one stationary roll chock and one movable roll chock could be used.

Rolls 16 are rotated by the drive mechanism shown in FIG. 5. A drive motor (not shown) supplies power to a drive shaft 45 which drives speed reducer 46. This speed reducer 46 may be of the worm wheel type which transmits power from the single input drive shaft 45 to a pair of speed reducer output shafts 47. These output shafts 47 are connected to spindles '48 by means of universal couplings 49. The spindles 48 are connected at the bottoms thereof to a second set of universal couplings 50 which drive rolls 16 through sleeved members 51 and roll shafts 52. Sleeved members 51 and roll shafts 52 each have a pair of fiat sides, as shown in FIG. 6, for driving engagement.

Slabs rolled according to this invention may be formed by any desired casting procedure. It is particularly advantageous to shape continuously cast slabs, because of the efiiciency and economy in carrying out casting and hot strip milling as a single continuous operation. However, the instant process is also applicable to slabs which have been formed by conventional ingot casting.

Most grades of steel can be satisfactorily edge rolled according to this invention. Low carbon steels, i.e., those containing less than about 0.12% carbon, are especially suited to this process. Other grades of steel, including stainless steel, can also be rolled. Non-ferrous metals such as titanium can also be rolled.

The present invention provides an improvement in planetary mill rolling processes which gives a planetary mill product in strip form which can be coiled and sold without edge trimming. Edge rolling according to this invention also facilitates scale removal and insures a slab of uniform width entering the planetary mill.

While this invention has been described with reference to specific embodiments thereof, it is understood that these embodiments are by way of illustration and the scope of this invention shall not be limited except by the claims.

What is claimed is:

1. In a method of producing metal strip from slabs, the steps comprising edge rolling a metal slab while at a temperature at least equal to that suitable for hot rolling of the metal, in a pair of grooved rolls defining a con- Vexly edged pass, dimensioned to be fully filled by the slab cross section, and introducing the edge-rolled slab directly into a planetary reducing mill, thereby converting the slab to hot-rolled strip while preserving thereon the convex edges characteristic of the slab after edge rolling, and eliminating lamination thereof.

2. A method as defined in claim 1, characterized by said rolls defining a pass effective to impart to each of the edges of said slab the cross-sectional shape of a dihedral angle from to having a curve as its vertex.

References Cited UNITED STATES PATENTS 2,254,629 9/1941 Stine 72-366 2,369,730 2/1945 Fisk 72235 CHARLES W. LANHAM, Primary Examiner.

A. RUDERMAN, Assistant Examiner.

US. Cl. X.R.

Disclaimer 3,422,656.-H0ward 8'. Orr, Up er St. Clair Township, Allegheny County, Pa. and. Anth D. Remhardt, South Holland, Ill. METHOD OF ROLLING LABS IN PLANETARY MILL. Patent dated J an. 21, 1969. Disclaimer filed Jan. 22, 1971, by the assignee, United States Steel Uorpowation. Hereby enters this disclaimer to claim 1 of said patent.

[Official Gazette May 235, 1971.] 

